Tweaks for new Objective-C API.

BUG=

Review URL: https://codereview.webrtc.org/1696673003

Cr-Commit-Position: refs/heads/master@{#11872}
diff --git a/webrtc/api/api.gyp b/webrtc/api/api.gyp
index 4fe8ce8..7f571c0 100644
--- a/webrtc/api/api.gyp
+++ b/webrtc/api/api.gyp
@@ -192,6 +192,13 @@
             'objc/RTCVideoTrack.h',
             'objc/RTCVideoTrack.mm',
           ],
+          # TODO(hjon): Make this compile without linking to libstdc++
+          # See https://bugs.chromium.org/p/webrtc/issues/detail?id=5593
+          'link_settings': {
+            'libraries': [
+              '-lstdc++',
+            ],
+          },
           'conditions': [
             ['OS=="ios"', {
               'sources': [